Food Contamination 101

There are three primary issues associated with biological contaminants in meat. These are the temperature at which the contaminant is killed, the amount of contaminant present, and the location of the contaminant.

The most common contaminants are E.coli and salmonella and they're both killed by heat at approximately 155F so heat the meat to above these temperatures and the meat will probably be safe to eat. But there's another issue involved: bacterial load.

Bacterial load refers to how many bacteria inhabit the meat. If the count is low (and what's "low" depends on the particular microbe) then the average healthy immune system can deal with the microbes on it's own. If the count is high enough then even with cooking some microbes will survive -- and if enough do they can take your immune system on. That said, if the heat is maintained for a length of time then more and more bacteria will die. Just as some humans will survive in 130-degree heat but the longer the heat is maintained the fewer humans will survive. So duration of heat is an issue as well if the food is heavily contaminated.

Another question is the location of the contamination. E.coli contamination occurs primarily during butchering when the meat is exposed to fecal material. This means the contamination exists on the surface of the meat. Heat the surface to 155F or higher (say, 160F) and even if the internal muscle is still raw you've killed the contamination. However, grind the meat up and you've mixed external contamination throughout the ground meat, hence hamburger should always be cooked to a temperature of 160F.

Salmonella, on the other hand, can inhabit the meat itself and so poultry, even if it's not ground up, should always be cooked to 160F. Salmonella can even be found within eggs.

Pork adds the danger of trichinosis, a parasite that inhabits the muscles. However, trichinosis is killed at 137F and so, cooking pork to an internal temperature of at least 143F will render the pork safe. But the truth is, trichinosis has been almost completely eliminated from our pork supply so the greatest threat with pork is the same as for beef and lamb: E.coli. Treat pork like you treat those meats and you shouldn't have any problems.

There are other contaminants that are associated with meat (such as campylobater and lysteria) but they're more rare and most of them are subject to the same treatments as those that eliminate the microbes listed above.

One last observation, industrial meat processing operations at both the farm level and packaging level greatly increase the risk of contamination. At industrial farms animals are gathered in close quarters and contamination spreads easily. At large packing plants there is less care taken to prevent contamination and microbes can easily spread from carcass to carcass. If you buy meat from small local producers you reduce the risk of contamination significantly.

Kevin Weeks is a Gather food correspondent (Paisano), personal chef, cooking teacher, and writer in Knoxville, Tennessee who spends too many hours on his feet, cooking. "Paisano" is a column focused on peasant dishes from around the world. To read more of Kevin's writings or connect to him click here. His blog, Seriously Good, is read by 75,000 cooks a month.